Robo-gigolo discloses the nature of condom failure

Researchers at Durex figure out why some condoms fail even when used correctly …

There is, perhaps, nothing quite like discovering that the safe sex you were engaged in was, well, not quite as safe as you tried to make it. Apart from the risk of pregnancy—a twenty year sentence of constant responsibility—the spread of potentially fatal sexually transmitted diseases make it quite important that safe sex is actually safe. As far as the prevention of sexually transmitted disease goes, nothing beats a condom. And yes, that includes abstinence, because when abstinence fails, all sex is unsafe, while a condom works whether you have sex or not.

Absolute numbers on the failure rate of condoms are very hard to obtain; estimates range between 0.4 and 6 percent, while a typical study involving 1000 condoms will usually result in something like ten or fewer failures. Nevertheless, the fact that there are failures is quite concerning, so researchers from SSL—they make Durex condoms—have been investigating sources of condom failure.

In the latest study, researchers examined condoms that had been returned by users after they failed—can you picture the unlucky intern's face?—to pinpoint the cause of failure. In addition, surveys were sent to customers who had complained about condom failure but not returned the condom, asking various questions about that particular sexual engagement. None of the condoms appeared to have failed due to manufacturing defects: the holes were too large to have passed quality control and there were no indications that other manufacturing defects might have been the cause of the defect. Furthermore, the survey respondents indicated that, among the spectrum of sexual practices, they were doing nothing unusual at the time, yet experienced similar styles of condom failure. (They were asked to draw pictures. No, we don't have copies.)

To ascertain the cause of the condom's failure, the researchers began stretching condoms over test-tube shaped forms. They found that, in general, it was difficult to cause a condom to fail, but there was one exception. If a condom was locally stretched and not allowed to recover before being stretched again for several iterations, it became fairly easy to rupture. Furthermore, the ruptures had characteristic traits, making it easy to identify the cause by simply looking at the failed condom. However, a test tube is not a penis. In order to find out if this source of failure could occur during intercourse, a sex robot was constructed. It consisted of a large rubber penis that was mechanically thrust into a variable-tightness rubber vagina.

The researchers found that local stretching and subsequent condom failure could be replicated by a combination of excess lubrication on the penis (inside the condom) and not enough lubrication outside the condom. They did not, however, report on the robot's satisfaction.

Chris Lee / Chris writes for Ars Technica's science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He lives and works in Eindhoven, the Netherlands.